1. Field
The present invention concerns a device for replacing one or more vertebrae, designed to maintain a spacing between two vertebrae.
2. Related Art
There is a similar device, known from the document US 2006/0200244, comprising a male part mounted inside a female part, an anchor shoe guided in translation and fixed in rotation on the male part, an anchoring surface on the female part, and a control element that transforms a rotational movement into a translational movement of the anchor shoe so as to bring the shoe into a first position in which the male and female parts are fixed relative to one another or into a second position in which the female and male parts can freely slide axially relative to one another.
That device has the drawback that the male part is axially fixed relative to the female part on only one side, which in the long run can be prejudicial to the quality of the joint between the male and female parts and thus to the safe use of the device.
There is another vertebral replacement device, known from the document U.S. Pat. No. 5,723,013, comprising an elastic-walled male part and a female part. The male and female parts comprise complementary notches in the form of asymmetrical serrations. These asymmetrical notches allow a distraction displacement of the male and female parts via a sliding of the notches of the male part into the notches of the female part and an elastic deformation of the wall of the male part, and compression-lock the male and female parts.
The advantage of such a device is that it is easy to adjust the distance between the male and female parts, since it simply requires distracting the male and female parts until they reach the desired position, this distracting movement being irreversible. However, the elasticity given to the male part can, over time, weaken the device and thus adversely affect its safe use. Moreover, because the outer sleeve of the male part cooperates directly with the inner sleeve of the female part, the diameters of these sleeves must be very precise, which complicates production.